Power hammer construction



Feb. 12, 1935. R, p rrz I 1,990,479

POWER HAMMER CONS-TRUCTI 0N Filed Feb. 25, 1932 2 Sheets-Sheet 1 W Fig. 1.

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Re mold PFiTg 'erold m WM Anya 1935. R. P. FITZGERALD POWER HAMMER CONSTRUCTION Filed Feb. 25, 1932 2 Sheets-Sheet 2 lnvenTor. Reginald P Fi'fggefqld EYW I QM I ATTys.

I 1 1 I J Patented Feb. 12, 193

UNITED STA 1,990,479 rowan HAMMER ooNs'raUorroN Reginald P, Fitzgerald, Braintree, Mass, assignor to Pneumatic Drop Hammer Company, Boston, Mass, a corporation of Massachusetts Application February 25, 1932, Serial No. 595,024

7 Claims.

This invention relates to improvements in mechanisms having a power cylinder provided with a piston and piston rod and means for supplying fluid under pressure to said cylinder to 5 actuate the piston in one direction, and the object of the invention is to provide means for gradually arresting the movement of the piston comprising a dash pot initially supplied with fluid under substantially the same pressure as that supplied to the power cylinder.

A further object of the invention is to provide a dash pot construction of the character above described in which means are provided to control the escape of fluid under pressure during the movement of the dash plunger.

Specifically, the invention relates to improvements in drop hammer constructions and comprises a dash pot operable gradually to resist the upward movement of the hammer at any predetermined stroke.

More particularly the object of the invention is to provide a drop hammer construction comprising a base frame, a hammer, and means operable by fluid under pressure to raise the hammer to a predetermined height, with a dash pot having a plunger subject to the fluid pressure acting upon the hammer operable when the hammer is raised to a predetermined position initially to resist upward movement of the hammer with substantially the full force of the fluid pressure acting upon the hammer, and operable upon further movement of the hammer by compression of said fluid to increase the effective force of such resistance and thereafter gradually to release said fluid under pressure as the hammer is brought to rest.

A further object of the invention is to provide fluid pressure means acting in co-operation with the fluid pressure acting upon the hammer to maintain the hammer in a desired raised position.

A further object of the invention is to provide a drop hammer construction in which the hammer is raised by fluid under pressure supplied to a power cylinder with a dash pot in axial alinement with the power cylinder, and means for introducing fluid under pressure into the chamber of the dash pot above the plunger head to resist the upward movement of the dash pot plunger and thereafter to supply fluid under pressure below the dash pot plunger for the purpose of maintaining the hammer in raised position.

These and other objects and features of the invention will more fully appear from the following description and the accompanying drawings, and will be particularly pointed out in the claims.

A preferred embodiment of the invention is illustrated in the accompanying drawings as ape plied to a drop hammer construction in which the hammer is secured to a piston rod having a piston reciprocably mounted in the cylinder and raised by fluid under pressure supplied to the cylinder beneath the piston, with suitable mechanism for actuating the valves controlling the supply of fluid under pressure to the cylinder and the exhaust of fluid therefrom to permit the hammer to drop. V

In thedrawings:

Fig. 1 is a side elevation of a power hammer embodying the invention;

Fig. 2 is an enlarged detail view, partially in section, of the power cylinder, the dash pot mechanism and the means for supplying fluid under pressure thereto; and,

Fig. 3 is an enlarged detail sectional View of a modified form of the dash pot construction.

The power hammer illustrated herein is similar in construction to that disclosed in my prior application Serial Number 518,351, filed February 26, 1931, for Power hammers, and the present application comprises in part a continuation of said application in respect to the mechanism for arresting the upward movement of the hammer, the power-arresting mechanism illustrated in Fig. 3 being substantially identical with that shown in my prior application aforesaid. The construction illustrated in Fig. 2 is amodifled and preferred form of the invention.

The power hammer construction illustrated in Fig. 1 comprises essentially a base 1 having an anvil member 2 supported thereupon, a frame mounted on said base comprising vertical col- 3 and 4 carrying at their upper ends a cylinder-supporting beam 5. The hammer 6, which is reciprocably mounted upon the columns 3 and 4, is secured to a piston rod, the upper end of which is connected to a piston reciprocably mounted in a cylinder 8 which is mounted centrally of the cylinder-supporting beam 5. Fluid under pressure is supplied from a suitable source, such as a tank 9, through a suitable pipe (not shown) to a valve box 10 from which it is conducted through a conduit 11, preferably formed in the cylinder-supporting beam 5 to the cylinder and to the dash pot in a manner which will hereinafter be described.-

Suitable mechanism is provided for actuating the valves in the valve box 10 to supply fluid under pressure to the cylinder 8 to raise the hammer, and to exhaust fluid under pressure therefrom to permit the hammer to drop, as will more fully appear from the disclosure in my prior application aforesaid.

As illustratedin Fig. 2, the cylinder-supporting beam is provided with an enlarged central portion or boss 12 having'a vertical central bore providing a dash pot cylinder 13 which desirably is provided with a suitable bushing 14. The

lower end of the bore terminates short of the lower end of the boss 12, thereby providing a lower head 15 for the dash pot which is integral with the beam. The dash pot is provided with an upper head 16 having an outwardly extending flange 1'7 which rests upon the upper end of the boss 12 and which also servesas the lower head of the cylinder 8. The cylinder 8 is mounted in a sleeve 18 having a lower annular flange 19 which is secured to the. cylinder-supporting beam by bolts 20 extending through the iange 19 of the sleeve, and the flange 17 of the head which is common to the cylinder and dash pot and anchored. in the cylindersupporting beam 5. The piston 21, which is reciprocably mounted in the cylinder 8, has a piston rod 22 which extends axially through the dash pot and is provided with an adjustable member, such as a stop or collar 23, adapted to engage the dash pot plunger whenthe piston rod and the hammer; which is secured to it, have been raised to a predetermined position.

The head 16, which is common to the cylinder and dash pot, is provided with a suitable packing 24 for the piston rod which is held in place by a plate 25 secured to the upper face of said head. The dash pot is provided with a suitable plunger having a head 26 which fits closely within the bushing 14 of the dash pot cylinder. The dash pot head has integral therewith a downward extension or sleeve 27 which is reciprocably mounted upon the piston rod 22 and extends well below the central boss of the beam which forms the lower head of the dash pot. The dash pot head is recessed to receive suitable packings 28 and 29 engaging respectively the bushing 14 and the piston rod, and an annular plate 30 secured to the piston head serves to hold the packings 28 and 29 firmly'in place. Thelower cylinder head is also recessed to receive a suitable packing 31 to prevent the escape of fluid under pressure from the dash pot.

Fluid under pressure is supplied to the power cylinder through a branch 32 leading from the conduit 11 in the cylinder-supporting beam through the flange 17 of the cylinder head 16 and through the flange 19 of the sleeve 18 to the cylinder 8. Another branch conduit 33 extending downwardly from the conduit 11 leads to a port '34 in the wall of the dash pot and its bushing 14. When the plunger head 26 is in lowered normal position it acts as a valve to close the port 34 leading to the dash pot cylinder. The head 16, which is common to the cylinder and dash pot, is provided with a preferably central port 35 of relatively small diameter establishing communication between the cylinder and the upper chamber of the dash pot.

7 Means are provided for adjusting the cross sectional area of the port 35, the preferred means shown being an adjustable set screw 36 extending inwardly through the head 16 into the port 35 and adapted to be adjusted in sucha manner as to throttle more or less the effective area of the port 35.

; In theoperation of the device above described the opening of the valves in the valve box ad mits fluid under pressure, preferably air under pressure, into the conduit 11 from which it passes through the branch 32 into the cylinder 8, thereby acting upon the under face of the piston 21 to raise the hammer. troduced into the cylinder 8 passes through the .Air under pressure thus inport 35 in the lower head 16 of the cylinder into the upper chamber of the dash pot, thereby filling it with air at the same pressure as that contained in the cylinder 8. The hammer gains in acceleration as it is moved upwardly by the force of air under pressure beneath the piston 21. When the hammer has been raised to a predetermined position the stop or collar 23 on the piston rod 22 engages the lower end of the sleeve 27 of the dash pot plunger thereupon propelling the plunger upwardly and rapidly increasing the fluid pressure in the dash pot cylinder 13, so that fluid under pressure will be forced therefrom through the port 35 into the cylinder 8 against the fluid pressure therein. The higher pressure created by the rapid movement of the dash pot plunger will obviously be in excess of the pressure lifting the hammer, thereby creating a greater force in the opposite direction to the lifting force. The force generated in the upper chamber of the dash pot; plus the force of gravity, being in excess of the lifting force, will gradually retard the upward movement of the hammer until the hammer comes to rest. 7

By controlling the size of the port 35, by adjustment of the set screw 36, varying pressures can be built up in the dash pot cylinder until the proper retarding action is obtained. To prevent the dash pot piston from forcing the piston rod and hammer downwardly the length of the plunger stroke, air is admitted to the lower chamber of the dash pot as soon as the plunger has begun its upward movement, as the upward movement of the plunger immediately uncovers the port 34 at the end of the branch 33 ofthe conduit which supplies fluid under pressure. The action of the air pressure on the under side of the plunger compensates an equal force of fluid pressure acting upon the same area on the upper face of the plunger. The effective areas upon which the fluid pressure acts upon the upper and lower faces of the plunger head are such that the force created by the unbalanced area, plus the weight of the head, will be less than the lifting force, thereby enabling the head to be maintained in raised position.

The fluid pressure introduced into the lower chamber of the dash pot cylinder co-operates with the fluid-pressure in the power cylinder 8 in maintaining the hammer in raised position after balance of pressure has been reached. When the hammer has been tripped by the proper movement of the valves to exhaust the air from the conduit ll, theair under pressure in the lower dash pot chamber also escapes through the conduit 11, thereby permitting the hammer to fall and the dash pot plunger to seek its original position. After the hammer strikes and the valves are so operated as again to supply air to the power cylinder to raise the hammer for another blow, airunder pressure will again be introduced into the upper chamber of .the dash pot cylinder, and in the event that the dash pot plunger has not fallen to its original seat, the pressure of the air entering the upper chamber of the dash pot from the cylinder 8 will, by reason of the increased area of the dash pot head upon which it acts, immediately force the dash pot plunger to its seat in proper position for operation when again engaged by the collar 23 upon the next upward movement of the piston rod 22 and the hammer carried thereby.

In the construction illustrated in'Fig. 3, the cylinder-supporting beam 5 is likewise provided with a'centi'alboss 37'which is bored downwardly from the top to provide a dash pot cylinder. The dash pot cylinder is provided with a cylindrical bushing 38. The upper end of the dash pot cylinder is closed bya head 39 having an annular flange 40. The sleeve 18 of the cylinder 8 is seated upon the flange 40 and is secured thereto by bolts 20 extending through the flange 19 of the cylinder sleeve, and the flange 40 of the head 39 into the cylinder-supporting beam as aforesaid. The head 39 is provided with a suitable packing 41 surrounding the piston rod 22. The dash pot cylinder is provided with a plunger 42 having a suitable packing 43 engaging thepiston rod and is provided with an integral cylindrical extension or sleeve 44; extending through the lower end of the boss 37 and adapted to be engaged by thestop or collar 23 which is adjustably mounted upon the piston rod when the piston rod has been raised to a predetermined height.

In this construction, as in that previously described, abranch 45 leads from the supply conduit 11 for fluid under pressure, to the cylinder, and another branch 46 leads frcm'the conduit 11 through the wall of the dash pot. In the construction disclosed in Fig. 3, the bushing '38 is provided with a port 47 communicating with the branch conduit 46 at a height slightly above the top of the plunger when the latter is in lowered position. When, therefore, fluid under pressure is supplied to the power cylinder 8, it will also be supplied through the port 47 into the upper chamber of the'dash pot.

In the construction illustrated in'Fig. 3, the wall of the dash pot is provided with a conduit 48 communicating at its upper end with the upper chamber of the dash pot near the upper end thereof, and at its lower end with the lower chamber of the dash pot a short distance above the bottom thereof, thus acting as a by-pass for the fluid under pressure. When the plunger is in its lowermost position the wall of the plunger acts as a valve to close the lower port 49 of the by-pass. When, therefore, the lower end of the plunger sleeve 44 is engaged by'the stop 23 upon the piston rod,'and the plunger is forced upwardly, the upward movement of the plunger is resisted by the full force of fluid under pressure in the upper chamber of the dash pot until the plunger has been forced upwardly a sufiicient distance to uncover the port 49, whereupon fluid under pressure in the upper chamber of the dash pot will be forced through the by-pass into the lower chamber thereof, from which it willescape through an annular channel 50 around the plunger sleeve into the atmosphere. The effective cross sectional area of the by-pass 48 may be controlled by an adjusting screw 51 seated in the wall of the boss 37 and extending into the by-pass 48; thus the resistance of the upward movement of the plunger, after the port 49 has been uncovered, may be suitably controlled to enable the upward movement of the hammer to be gradually arrested.

In each of the constructions above described such adjustment may be made as gradually but rapidly to check the upward movement of the hammer before the stop or collar 23 upon the piston rod forcibly strikes the under face of the central boss upon the beam, thereby avoiding any shock to the frame, although after the hammer power hammers or of power cylinders of the type above described the supply of air under pressure to the cylinder is' substantially discontinued before the collar 23 engages the end of the plunger sleeve, and that the upward movement of the hammer, piston rod and piston, which it is necessary to check, is that due to the momentum of the hammer acquired during its upward movement and such additional force as is produced by the expansion of the fluid'under pressure in the cylinder after the supply has been substantially cut off. I

It will be obvious that whereas in the preferred embodiments of the invention disclosed herein the cylinder of the dash pot is shown and described as formed in the cylinder-supporting beam in axial alinement with the power cylinder, that the dash pot may be constructed independently of the cylinder-supporting beam and secured thereto either in axial alinement with the cylinder or independently thereof.

It will also be obvious that the dash pot mechanism for arresting the upward movement of the hammer may be applied to other types of hammers than those in which the hammer is raised by fluid under pressure. 'The particular embodiments of the invention shown and described herein are, therefore, of an illustrative character and not restrictive of the meaning and scope of the following claims.

Having thus described the invention, what is claimed as new, and desired to be secured by Le ters Patent, is: I

1. In a drop hammer construction comprising a base and anvil, a frame having an overhead supporting beam, a dash pot cylinder therein, a power cylinder and piston mounted on said beam having a piston rod extending axially through said dash pot cylinder, a hammer connected to said piston rod, a dash pot plunger reciprocably mounted on said piston rod having a sleeve rigid therewith extending downwardly through a bearing in the lower head of said dash pot cylinder, a stop on said piston rod to engage said plunger sleeve when the hammer has been raised to a predetermined height and to raise said plunger upon further upward movement of said hammer, means for supplying fluid under pressure to said power cylinder to lift said hammer, and means for also supplying fluid under pressure from the same source of supply to the chamber of said dash pot above said dash pot plunger to resist upward movement of said plunger when engaged by the stop on said piston rod.

2. A drop hammer construction comprising a base and anvil, a frame having an overhead supporting beam, a dash pot cylinder therein, a power cylinder and piston mounted on said beam having a piston rod extending axially through said dash pot cylinder, a hammer connected to said piston rod, a dash pot plunger reciprocably mounted on said piston rod having a sleeve extending through a bearing in the lower head of said dash pot cylinder, a stop adjustably mounted on said piston rod to engage said plunger sleeve when the hammer has been raised to any selected height and to raise said plunger upon further upward movement of said hammer, means for supplying fluid under pressure to said power cylinder to lift said hammer, means for also supplying fluid under pressure from the same source of supply to the chamber of said dash pot above said plunger, and means for supplying fluid under pressure to the chamber of the dash pot Y raised position.

below the head of said plunger during the upwardmovement of said plunger operablein co operation with the fluid pressure in the power cylinder to maintain the hammer in a definite 3. A drop hammer construction comprising a base and anvil, a frame having an overhead supporting beam, ardash pot cylinder therein, a powercylinder mounted on said beam in axial alinement with said dash pot cylinder and have ing a cylinder head common} therewith provided with a relatively small port establishing. comheight, and a conduit for supplying fluid under pressure to said power cylinder.

. 4. A drop hammer construction'comprising a base and anvil, a frame having an overhead supporting beam, a dash pot cylinder therein, a power cylinder mounted on said beam in axial alinement with said dash pot cylinder and having a cylinder head common therewith provided with a relatively small port establishing communication between said cylinder and dash pot, means for adjusting theeflective cross sectional area of said port, a piston in said cylinder having a piston rod extending axially through said dash pot cylinder, a hammer connected to said piston rod, a-dash-pot plunger reciprocably mounted upon said piston rod and having a sleeve integral therewith surrounding said piston and extending 7 of said dash pot below said dash pot plunger having a port which is normally closed by said dash pot plunger, but opened upon upward movement of said plunger to supply fluid under pressure to the chamber of the dash pot below said plunger, thereby acting in co-operation with the fluid pressure in said power cylinder to maintain the hammer in a predetermined raised position.

5. A drop hammer construction comprising a base and anvil, a frame having an overhead sup porting beam, a dash pot cylinder therein, a power cylinder and piston mounted on said beam having a piston rod extending axially through said dash pot cylinder, a hammer connected to said piston rod, a-dash pot plunger reciprocably mounted on said piston rod having a sleeve extending downwardly through, a bearing in the lower head-f said dash pot, a stop on said piston rod to engage said plunger sleeve when the hammer has been raised to a predetermined height and to raise said plunger upon further upward moveme'ntof said hammer, means for supplying fluid under pressure to said power cylinderand to the chamber of said dash pot above said,

hammer, means operable by the upward movement of said plunger respectively to cut off the supply of fluid under pressure to the chamber of said dash pot above said plunger and gradually to hammer.

6. A drop hammer construction comprising a, base and anvil, a frame having an overhead sup;

porting beam, a dash pot cylinder therein, a power cylinder and piston mounted on said beam having a piston rod extending axially through said dash pot cylinder, a hammer connected to said piston rod, a dash pot plunger reciprocably mounted-on said piston rod having a sleeve extending. downwardly through a bearing in the lower head of said dash'pot, an adjustable stop on said piston rod'to engage said plunger sleeve when the hammer has been raised to a predetermined height and to raise said plunger upon further upward movement of said hammer, aconduit for supplying fluid under pressure to said powercylinder having a branch I communicating with said dash potjat a predetermined distance above its plunger when the latter is in its lowest position and adapted to beclosed by said plungerv upon upwardmovement thereof, and a restricted by-passleading from the upper chamber of said dash pot to thelower chamber there of and normally closed at its lower end by the dash pot plunger when-in-its lowest position, the

construction being such that upon upward movement of said plunger the supply of fluid under pressure to the lower chamber of the dash not will be cut off and upon continued movement of said plunger the lower end of the by-pass will be opened to release the fluid under pressure gradually from the upper chamber of the dash pot.

7. A drop hammer construction comprising a base and anvil, a frame having an overhead supporting beam, a dash pot cylinder therein, a power-cylinder and piston mounted on said beam having a piston; rod extending axially through said dash pot cylinder, a hammer connected to said pistoh rod, a dash pot plunger reciprocably mounted on said; piston rod having a sleeve.ex-.- tending downwardly through a bearing in the lower head of said dash pot, an adjustable stop on said piston rod to engage said plunger sleeve when the hammer has been raised to a predetermined height' and to raise said plunger upon further upward movement of said hammer, a conduit for supplying fluid under pressure to said power cylinder having a branch communicating with said dash pot at a predetermined distance above its plunger when the latter is in its lowest position and adapted to, be closed by said plunger upon upward movement thereof, a restricted by-pass leading from the upper chamber of said dash pot to the lower chamber thereof and normally closed at its lower end by the dash pot plunger when in its lowest position, the construction being such that upon upward movement of said plunger the supply of fluid under pressure to the upper chamber of said dash not will be cut oh and continued movement of said plunger will gradually force the fluid under pressure from theupper chamber of said dash pot, and adjustable means for varying the effective cross sectional area of said by-rpass, whereby the rate of escape of fluid under-pressure from said dash pot maybe controlled.

REGINALD P. FITZGERALD. 

